Loss and Grief
To the ones facing the loss of a loved one, there are a number of issues to address. If they vanished, you can be assured of their well being... they were taken to Heaven to be with their Savior, Jesus Christ. The young children are not yet accountable for their own souls, as they simply are not old enough to understand the issue of sin, and the need for a Savior. God in His mercy has delivered them from the judgments coming on the earth.
If your loved one was killed in some accident, and the body is still there, what a tragedy that is. Salvation in Jesus Christ is the assurance of eternal life. A body remaining is a soul that did not go to heaven, along with the rest of believers at the Rapture. There is hope, however, that the one who died as a result of his injuries may have called out to God in saving faith in the last moments of life. He may have realized that the Word of God is indeed true, and prayed the sinner's prayer before the last breath of life left him.. God alone knows. Here, we see the importance of believing what the Bible has to say about matters of life and death. Often in the past you may have heard the question, "If you died today, where would your soul go?" Now you see it is not a trifling matter after all.
Look to God's word for understanding, and to His Son Jesus Christ for salvation. All the material things in the world cannot satisfy the soul like Jesus. There is a God-sized hole in the heart of every human that can only be filled with Christ... apart from which nothing will ever make sense in the aftermath of this event. Believers understood this and lived life with the blessed assurance of eternal life. Now, that eternal life is realized in full, and you can rejoice that your loved one is finally at home with the Lord. Now it's your turn to trust in Christ, and gain the hope of one day being reunited with them in Heaven.